function s1_generate_a_series_of_files() {
   for i in {1..100};do echo $i>/tmp/new_file$i;done
}

function s2_list_4_files_in_long_format_about_account_and_group() {
   ls -l /etc/{passwd,shadow,group,gshadow} |sort -d
}

function s3_find_items_related_to_given_username(){
   grep -h $1 /etc/{passwd,shadow} |sort -d
}

function s4_find_items_related_to_given_group_name() {
   grep -h $1 /etc/{group,gshadow} |sort -d
}

function s5_create_groups_for_given_group_names() {
   groupadd rnd && groupadd itoperation
}

function s6_create_users_and_set_their_group_as_required() {
   useradd -G rnd adam && useradd -G rnd bob && useradd -G itoperation calvin && useradd -G itoperation david && useradd -G rnd edward
}

function s7_change_users_shell() {
   usermod -s /usr/bin/sh adam && usermod -s /usr/bin/sh edward
}

function s8_set_password_change_policy() {
   passwd -n 10 -x 60 -w 10 adam
   passwd -n 10 -x 60 -w 10 bob
   passwd -n 10 -x 60 -w 10 david
   passwd -n 10 -x 60 -w 10 calvin
   passwd -n 10 -x 60 -w 10 edward  
}

function s9_set_password_for_five_users() {
   usernames=(adam bob david calvin edward)
   for i in $(seq 1 5);do echo ${!i};echo $(($i-1));done
   echo "${usernames[0]}:$1" | chpasswd
   echo "${usernames[1]}:$2" | chpasswd
   echo "${usernames[2]}:$3" | chpasswd
   echo "${usernames[3]}:$4" | chpasswd
   echo "${usernames[$(( $i-1))]}:$5" | chpasswd
}

function s10_lock_bobs_password() {
   usermod -L bob
}

function s11_include_adam_into_wheel_group(){
   usermod -a -G wheel adam
}

function s12_change_files_permission() {
   for i in {1..30};do chmod -R 640 /tmp/new_file$[3*i];done
}
